Sliding windows such as double hung have won worldwide application for many types of residential and commercial structures, various types of vehicles, boats, flying apparatus, etc. Sliding windows have acquired such a universal popularity in part because they are convenient and save space, they provide easy and suitable access and have many other advantages.
Usually the sliding windows consist of a pair of window sashes, preferably equal in size, each of which moves independently along the parallel tracks that are contained within the inner sides of a single frame that is built into or installed the designated places in the wall. The movement of the sliding windows relative to each other, and both of them relative to the mutual frame on which they are mounted, may be either in horizontal or vertical direction. In order to close such windows, if windows slide in vertical direction, the sash of one window should be pushed upward until it presses against the frame, and the other one pulled downwardly.
The locking function of the sliding windows is provided by the latch which is usually mounted on the sashes of the windows and has two interrelated parts. The location of the latch depends on whether the windows slide in the horizontal or vertical direction relative to each other. If the windows slide in the vertical direction, one portion of the latch is located on the top surface of the lower stile of the upper sash, and the counterpart of the latch is on the top surface of the upper stile of the lower sash. When both windows are closed, both parts of the latch face to each other and are ready to engage. One part of the latch, which may be called the locking member, usually contains a handle which extends outwardly from the window sash. The handle is firmly connected to a cam. The cam has a rounded groove cut to accommodate the key located on the keeper portion of the latch which is affixed to the sash of the second window. The radius of the groove gradually reduces from the beginning of the groove toward the end. Thus, when the handle of the latch is moved from an unlocked to a locked position, the cam starts to wrap around the key of the second window until the key is pressed against the inner wall of the groove. The further key moves into the groove of the cam, the more pressure the key causes to the inner wall of the cam. Eventually, because of such increased pressure, the handle tends to stop in certain position and the latch is locked.
Because of the configuration of the sliding windows, there is a possibility to reach the latch from outside when the windows are closed. Such access provides the opportunity for unwanted breaking into the premises behind the sliding windows. The present invention provides a security and offers to minimize the possibility of such forced entry. The mechanism of the latch is designed in such way that reduces the possibility of opening the latch from the under side of the sashes. The positioning of cams embodied in this invention relative to each other and their configuration makes it difficult for unauthorized person to disengage the locking cam even having access to the latch from underneath the sash lock. In addition, this mechanism may be completely covered by the hood which extends from the outer shell or housing of the latch, providing additional protection against forced unwanted accessibility to the latch. Therefore, it would be advantageous to supply sliding windows with the latches that embody the present invention.